The present invention is directed to a pyrodetector for the detection of a body which has a temperature differing from that of the environment and includes a concave mirror having a great circle and a sensor which has electrical connections arranged in a circular arc concentric with reference to the great circle of the mirror on a pyro-electric foil with the circular arc coinciding with the plane of the directional selectivity.
An infrared detector is disclosed in U.S. Pat. No. 4,225,786, whose disclosure is incorporated by reference. The detector of this patent has a spherical mirror and a sensor which is constructed to extend over a circular arc and which is located on a heat-insulating carrier. The arc of the sensor is a circular arc coaxial with the spherical mirror and comprises the distance of the focal length F from the mirror surface of the spherical mirror. One embodiment of this sensor has a centrally arranged sensor element and respectively additional sensor elements arranged laterally therefrom which are connected in parallel and are connected in a bridge relative to the centrally arranged sensor element. Otherwise, the sensor of this patent is a single sensor element extending over a circular arc. This arc-shaped sensor and the spherical mirror defines the reception direction characteristics of the known detector which is wide-angled with reference to the plane of the arc and is potentially only slightly wide-angled by contrast in a direction perpendicular thereto For example, a polyvinylidene fluoride (PVDF) foil is provided for the sensor and this has the pyro-electrical properties. Given temperature modifications of the material of the foil, the electrical voltage can be taken between two electrodes, which are arranged on two opposite surfaces of the foil, and the voltage will change in response to the degree of the temperature modification. In applications of a pyrodetector, the foil, or one and/or the other electrode as well, is used as an absorption surface for heat radiations so that the signal to be taken at the electrode is measured for the absorbed heat.
A pyrodetector that has a strict directional characteristic is disclosed in U.S. Pat. No. 4,404,468, whose disclosure is incorporated by reference. This pyrodetector comprises a parabolic mirror in which two sensors differing in function are arranged. The one sensor is positioned in the focal point of the parabolic mirror and serves the purpose of detecting the radiation of a subject. The other sensor serves as a temperature compensator and is arranged outside any and all focal points of the mirror for radiation incident from the intended direction. The pyrodetector, thus, has a single focal point detector for detection of any and all signal heat radiations of a subject to be detected which is to be received.
The sensor of this known pyrodetector is a PVDF foil comprising electrodes situated thereon which are employed for the signal pick-up in the way already set forth hereinabove. This sensor, which is flat, can be arranged in the pyrodetector so that the radiation reflected in the parabolic mirror proportionally impinges the two surfaces of the foil so that the plane of the sensor coincides with the central axis of the parabolic mirror. This axis is also tee axis of the single reception direction for the detector.